Role of Two Different Silane Coupling Agent on Wood Carbon / General
Purpose Unsaturated Polyester Particulate Composites
N. Prabu1, Mansur Ahmed
1 and S. Guhanathan
2,
1 PG and Research Department of Chemistry, Islamiah College (Autonomous),
Vaniyambadi – 635 752, Tamil Nadu, India.
2 PG and Research Department of Chemistry,
Muthurangam Govt. Arts College, (Autonomous),
Vellore – 632 002, Tamil Nadu, India.
Abstract The present investigation was to evaluate the effect of silane coupling agent on the spectral, thermal,
morphological and hardness properties of four different carbon viz., rose , neem , ground net, teak prepared from
agricultural waste along with general purpose unsaturated polyester resin (GPR) particulate composites were made
using casting technique. The incorporation of coupling agent into the carbon/polyester composites were clearly
noticed using the FTIR spectroscopy. The properties of the composite with and without coupling has also been
investigated and compared. A result of the studies implies that amino propyl trimethoxysilane treated composites
are experiences excellent properties than vinyl triethoxy silane treated composites and untreated ones.
INTRODUCTION A composite material is made by combining
two or more materials to give a unique combination
of properties. Composites based on a polymer matrix
have become more common and are widely used in
many industries due to the advantageous properties
offered by the polymers. Filling polymers with
mineral dispersion has long been a practice in the
plastic industry as a way to reduce overall production
costs and enhance certain properties.1 generally; most
mineral fillers used in thermoset and thermoplastic
composites are ground into fine particles with
relatively low aspect ratios. The low aspect ratios and
relatively low price of the fillers are very attractive in
a plastics market that grows more and more
competitive.1 Almost any powdered material can be
used as filler, the common ones being obtained from
natural deposits. Of the several hundred fillers used,
those that find widespread use are various grades of
calcium carbonate, quartz, mica,2 silica flour, talc,
3
and various clays.4 The utilization of as an additive
component in polymer composites has received
increased attention recently, particularly for price-
driven/high-volume applications.5 Srivastava and
Shembekar6 evaluated tensile and flexural properties
of fly-ash-filled epoxy resin, and they reported that
the loading of FA in epoxy–resin causes a decrease in
the tensile and flexural properties of the composites.
A wide variety of fillers have been incorporated in
pure polypropylene (PP) to impart flow and
mechanical properties and to reduce costs.7 Chand
and Gautham8 developed composites of FA and glass
fiber with polyester resin and re-ported their abrasive
behavior and wear loss. Coutinho et.al.9 prepared a
composite of fiber/PP and found a decrease in
mechanical properties. Many studies have been
published concerning the processing conditions and
properties of thermoplastics with fiber,10–13
glass
fiber,14,15
mica,16
and calcium carbonate.17
Unfortunately, the better stiffness obtained through
filling is often accompanied by drawbacks such as
lower processibility and lower toughness.
Enormous amount of research work focuses
on various fillers on unsaturated polyester composite
were found to have deteriorated in overall properties
of the composites. To our best of knowledge, no
work has been reported on the carbon prepared from
agricultural waste. This development has been
brought about because the incorporation of carbon
from renewable offers several advantages; because it
is the best way to dispose the environmental waste
carbon. It is a fine and powdery material. The fillers
have been shown to increase the stiffness of the
composites, but the strength, however, suffers a
setback.18
To overcome these problems, a variety of
methods have been adopted, including the choice of
processing aid and modification of the filler surface.
Based on the reasoning that a proper interlayer results
in a balance between toughness and strength, the
efforts has been noticed in the developing of new
coupling agents (CAs) for the fillers during the past
decade.19–21
The properties of a composite, such as
strength and modulus, are important factors for
producing high-quality composites. Many researchers
have tried to improve the adhesion between filler and
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matrix resin by chemical reaction with CAs. Silane
CAs are generally considered to be adhesion
promoters between mineral fillers and organic matrix
resins and, as such, provide improved mechanical
strength and chemical resistance to the composites.22
One of the authors, previous contribution reported
that a 40% loading of FA caused minor strength
reductions of filled polyester resin, whereas loading
beyond 40% caused a drastic deterioration of
properties. Based on the above discussions, authors
aims to describe the various carbons viz., rose , neam
, ground nut, teak carbons into the unsaturated
polyester resin and the influence of two different
silane-based CAs on the mechanical, thermal,
morphological properties of carbon / polyester resin
with maximum of 40% loading have been discussed.
EXPERIMENTAL
Materials General purpose unsaturated polyester resin
(GPR) is composed of maleic anhydride, iso-phthalic
anhydride, aliphatic diol, styrene monomer, 1%
solution of methyl ethyl ketone peroxide (catalyst),
1% solution of cobalt–naphthenate (accelerator), and
surface-modified calcium carbonate filler (120–150
m, bulk density 0.7289 g/cc) were obtained from
Sakthi Fiber Glass Ltd., (Chennai, India). The carbon
prepared from various renewable sources like Rose ,
Neem , Ground nut, Teak in a pre-dried powdered
form were used as filler. CAs, Amino
propyltrimethoxy silane (AMPS), and
vinyltriethoxysilane (VES) were obtained from
Sigma-Aldrich (St. Louis, MO). Methanol from Avra
synthesis private Ltd. (Hyderabad, India) was also
used in this investigation.
Characterization of carbon: The carbon was characterized for the
following properties: moisture content, loss on
ignition, pH, and bulk density. The notations of
various carbon and there composites are presented in
Table I. The results are given in Table II. The
particle size of the and their concern carbon were
determined by sieving through a suitable sieve
(standard test sieve BSS 40 to 425µm and 60 to 250
µm). The carbon with particle sizes in the range of
60-250 µm was used in this study.
TABLE - I
CHARACTERISATION OF CARBON
TABLE – II
PARTICLE SIZE WOOD POWDER AND CARBON
NAME OF
THE WOOD
PARTICLE SIZE OF
WOOD POWDER (%)
(BSS 40 - 425µm)
PARTICLE SIZE
OF CARBON %
(BSS 60 - 250µm)
Teak Wood
88.0859
70.5657
Groundnut
35.0112
57.3495
Neem Wood
64.5647
63.3031
Rose Wood
53.2606
69.6921
Parameter
Concentration
(Average)
C1 C2 C3 C4
Moisture content (%) 6.4587 6.9508 5.8537 7.2376
Ph 7.4000 7.200 7.6000 7.1000
Bulk density (g/cc) 0.8487 0.7437 0.8678 0.7982
Loss on ignition (%) 0.9566 0.8506 0.7543 0.8592
Sulfate content (%) 0.2023 0.2961 0.3333 0.1307
Chloride content (%) 0.3090 0.3292 0.4210 0.3828
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Treatment of carbon with CAs: A 5% solution of APMS and VMS in
methanol was prepared. A 5% solution (11 mL)
mixed with 40 wt % of dried carbon in a closed
container was shaken for 20 min in a mechanical
shaker and kept as such for 20 min. This surface-
treated carbon contained 0.5% CA by weight.
Similarly, 1.0 and 2.0% CA loaded carbon mixtures
were prepared by taking 22 and 44 mL of CA
solution with 40 wt % of dried carbon.
FTIR The infra-red spectra were recorded on a
Spectrum One (Perkin Elmer) in the range between
4000 - 400 cm-1
. The samples were analyzed as
powders.
MORPHOLOGICAL STUDIES Scanning Electron Microscopic (SEM)
studies were carried out using VEGA3 TESCAN,
CRANBERRY TWP, USA.
THERMAL STUDIES TGA analyses were conducted using a TA
Instruments SDT Q600 V20.9 Build 20 thermal
analyzer, using constant heating rate (200C/min) from
room temperature to 5000C.
X-ray diffraction:- X-ray diffraction patterns were obtained
using a Bruker D8 advance diffractometer equipped
with a Cu source (wavelength 1.54 nm) operating at
40 kV and 40 mA. Scanning rate was 0.020 s
-1 from
2θ = 20 to 20
0 for various carbon samples and 2
0 to
400 for calcium carbonate samples to check for
alteration in the characteristic diffraction peaks of the
material.
Hardness studies The hardness was measured with a hardness
tester (Kobunshi Keiki Co., LTD., Japan), as per
ASTM D 2240-68 at CIPET – Chennai. It was
determined by forcing a hard indenter into the surface
of the material. The average of five hardness readings
were consider for each samples calculation.
Results and discussion
Effect of CAs on the FT-IR of the
composites Figure (1 - 8) FT-IR spectrum of APMS and
VES treated carbon shows the presence of
absorption peaks at 1283 cm-1 and 1727 cm-1,
which may be assigned to asymmetric C-O and C=O
stretching vibrations of ester bond. The peaks
appearing at 2980 cm-1
, 2850 cm-1
and 1370 cm-1
also
confirm the formation of SiOCH2CH3 and Si(CH2)3
stretching frequencies. Similar to our observation,
Alagar et.al23
was also observed for system. The peak
at 3425cm-1
which has been related to OH stretching
frequency of Si-OH group present in the coupling
agent AMPS. These peaks also overlap with amine
peak from the coupling agent (REF). This suggests
that a part of the silane was hydrolysed and reacted
with carbon surface. A.E. Langroudi et.al24
also
observed similar to our observation on aminopropyl
trimethoxy silane treated copper/epoxy composite
system. Some of the peaks mentioned in the spectrum
clearly indicated that the organic fractions (from
coupling agent) have strongly been associated over
the carbon surface in the coupling agent treated (C1,
C2, C3, C4) / GPR composites.
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Effect of CAs on the SEM of the
composites In order to study the morphology of C1, C2,
C3 and C4 with GPR composites examined by SEM
studies were shown in Fig (9 - 20). These samples
were subjected to Ag/Pd coating to render these
conductive before examination. Polymer rich phase
was shown in the top. SEM images of the so-obtained
composites attested to have fine interfacial adhesion
between renewable carbon and the polyester chains.
Table (4a and 4b) Summaries the hardness of the
carbon/GPR composite treated and untreated
coupling agent. The microstructures of untreated
composites show some aloofness of filler from
matrix. This indicated the insufficient bonding
between polyester and wood carbon as filler and less
adhesion occurred between them. Hence, the results
of hardness clearly indicate that pure GPR has
hardness value of 70.3, whereas the hardness value
found to have 81.5 for C1, 78.3, 70.0 and 79.2 for
C2, C3 and C4 in respect of untreated carbon. This
may be clear that the incorporation of fillers enhances
resistance towards penetration over GPR. This might
be due to the proper intimate mixing of renewable
carbon with the polyester resin were shown in figure
(9 - 20). However, on further surface treated with
two different coupling agents hardness was also
increased. This might be due to the surface treated
composites exhibits renewable carbon is better
dispersed in the GPR. The presence of coupling
agents less detachment and agglomeration of wood
carbon in polyester matrix thus enhanced wet ability
between renewable carbon and polyester. The effect
of improve interfacial bonding between the filler and
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the matrix. Our earlier observation, 25
was also
supported for increase of the hardness for untreated
to treated carbon/ GPR composites.
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Effect of CAs on the Thermal studies of
the composites The thermal stability of the untreated carbon
and APMS and VES based surface treated carbon
GPR composites were presented in Fig. 21 – 32
which summarizes the TGA data on GPR, untreated
carbon (C1-C4) followed by two different coupling
agent (APMS and VES) treated carbon (C1-C4)
composites. In general, all thermo grams shows two
stages of decomposition were observed for all
composites. The 10% weight loss was observed at
276oC for GPR, 210, 195, 210, and 210
0C in respect
of untreated C1, C2, C3 and C4 respectively. Almost
similar observation was observed for coupling agent
treated C1-C4 viz., 210, 180, 200 and 2000Cfor
APMS and 220,210,235 and 2250C for VES. The
50% weight loss was found to have around 4640C for
GPR, nearly 14 and 21% lesser than the weight of
GPR have been observed for untreated C1-C4 and
surface treated C1-C4 correspondingly. In overall
observation for all composite in respect of thermal
studies is concern, GPR has thermally stable than
untreated and surface treated carbon. Effect of
surface treated over the carbon was found to be very
minimal.
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TABLE – III-a
TGA FOR C1, C2, C3 & C4-APMS-GPR
% of Wight loss 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
GPR 276 374 392 406 464 538 620 - - -
C1-AMPS-GPR 210 295 345 360 370 385 390 410 - -
C2-AMPS-GPR - 25 280 290 330 350 370 380 390 420
C3-AMPS-GPR - 25 200 290 330 360 365 380 390 405
C4-AMPS-GPR - 25 200 295 337 355 370 380 387 415
TABLE – III-b
TGA FOR C1, C2, C3 & C4-VES-GPR
% of Wight loss 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
GPR 276 374 392 406 464 538 620 - - -
C1-VES-GPR 220 315 350 365 380 385 390 420 - -
C2-VES-GPR - 25 210 300 350 355 372 375 383 410
C3-VES-GPR - 30 235 320 350 367 375 387 390 410
C4-VES-GPR - 25 225 310 337 362 370 375 385 410
Effect of CAs on the X-ray Diffraction of
the composites Studies of amorphous materials represent a
large and important emerging area of materials
science. It is an area which is not amenable to the
most of the conventional theoretical techniques of
solid-state physics as there is no periodicity to
simplify the mathematics. Due to the lack of
periodicity, extraction of structural information from
amorphous materials becomes very difficult. In this
work we have used XRD technique to analyze the
variations of the structural parameters of amorphous
carbon due to irradiation. XRD is a very useful and
simple technique to understand the structural details
of the solid-state substances. Incident X-ray interacts
with large volume of the material at a time and an
average property of the material can be characterized
rather than the local property. This makes XRD a
powerful technique for studying the disordered
materials which is inherently heterogeneous and
where the estimation of average property has got
practical significance.
Fig (33 - 44) summarizes the XRD pattern
of composites shows amorphous pattern for pure
GPR, untreated carbon(s) viz., C1, C2, C3 and C4 as
well as APMS and VES surface treated C1, C2, C3
and C4 composites. The untreated C1 has the d
spacing at 4.268 with A = 20.7920, whereas APMS
and VES treated C1 has d spacing at 3.36148 and
1.54624, A = 26.4950
& 59.7590 and d = 7.60613,
3.4144, A = 11.6250, 26.676
0. This was clear that the
additional d spacing may be due to the incorporation
of organic moieties like AMPS and VES over C1.
Similarly for C2, C3 and AMPS, VES treated d
spacing values at 3.37, A = 26.4170, 3.36148 and
1.54624, A = 26.4950
& 59.759, 7.60613, 26.6760,
3.38, A = 26.6810, 7.58, 5.28, 4.29 & 1.547, A =
11.6610, 16.768
0, 20.684
0, 59.701
0¸ 7.615, 5.240,
4.297, 3.0742, A = 11.610, 16.906
0, 20.652
0, 29.022
0,
3.4144, A = 11.6250, 4.8526, 3.353, A = 18.267
0,
26.5620,
7.625, 4.282, A = 11.5960, 20.725
0
respectively. The presence of peak was not observed
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in diffractogram of composition C4-GPR composite
which may indicate delamination of carbon added
during polyester fabrication. Similarly to our
observation Michal Kedzierski et-al,26
was identified
for the polyester/MMT nano composites preparation
using intercalative copolyaddtion reaction. However,
APMS and VES surface treated C4 found to have the
d spacing at 1.326, A = 71.0310, 7.623, 4.303, 1.826,
A = 11.5980, 20.620
0, 49.881
0 respectively. This
might be due to surface treatment protected the
delamination of carbon C4 during polyester
fabrication. Further, the incorporation of coupling
agents APMS and VES into various carbons (C1 to
C4)
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Effect of CAs on the hardness of the
composites The durometer hardness values of the
various composites made in this study are given in
Table.4. From the Table 4, it was clear that 15%, 12
%, almost level, and 12 % for C1, C2, C3 and C4
respectively. The values indicate that the mineral-
filled composites were harder than the unfilled
composites. The surface modification further
increased the hardness. This observation is in
agreement with the fact that the hardness is a measure
of resistance to penetration. This resistance to the
penetration of GPR increased when filled with the
mineral carbon, and still more resistance was offered
by the material when the surface of the filler was
modified with CAs for improved compatibility
between the filler and the matrix.
TABLE – 4- A
HARDNESS FOR CARBON – APMS – GPR:
HARDNESS
TEST GPR
C1-APMS-
GPR
C2-APMS-
GPR
C3-APMS-
GPR
C4-APMS-
GPR
10% 70.2 76.8 77.6 75.6 74.9
20% 70.5 82.1 84.5 78.5 77.8
30% 70.6 84.0 86.0 81.2 78.6
40% 70.3 86.5 87.8 83.0 80.3
TABLE – 4 – B
HARDNESS FOR CARBON – VES – GPR:
HARDNESS
TEST GPR
C1-VES-
GPR
C2-VES-
GPR
C3-VES-
GPR
C4-VES-
GPR
10% 70.2 74.2 75.7 77.5 79.9
20% 70.5 81.0 82.4 80.0 82.8
30% 70.6 82.4 83.8 81.9 84.6
40% 70.3 84.8 85.1 84.0 85.8
CONCLUSIONS Based on the carefully analysis of the date the
following conclusions were made.
o Wood carbon composites were
fabricated with and without treated
incorporation of coupling agents
into wood carbon polyester were
noticed using FT-IR Spectroscopy.
o The results of SEM images of
untreated and surface treated wood
carbon polyester was reveals that
the perfect wetting and less
detachments was observed for
surface treated wood carbon
perhaps, there was aloofness was
noticed for untreated carbon.
o The result of the thermal studies
shows GPR has thermally stable
than the untreated and surface
treated carbon. The effect of
surface treated and the carbon
found to be very minimal.
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o The XRD pattern of all treated and
untreated wood carbon composites
shows amorphous in nature.
o The improved hardness was
observed coupling agents modified
wood carbon than untreated wood
carbon composites in overall
observation APMS treated
composites has better influence
than VES treated composites in all
properties.
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